The present invention relates to a mono-filament of a vinylidene fluoride resin (hereinafter sometimes expressed as "PVDF") having a remarkably improved abrasion resistance as well as satisfactory knot strength and tensile strength, and a process for producing the same.
A PVDF monofilament is excellent in knot strength and tensile strength in addition to weather resistance and is therefore suitable as a material for fishing lines, fishing nets, ropes, etc. In the use such as a fishing line, however, an abrasion resistance is important in addition to the above-mentioned physical properties, since it is rubbed with rockes, float rubber, etc.
As processes for producing PVDF monofilaments, several processes have been proposed, such as a process wherein stretching and heat fixation after melt spinning is effected at 80.degree. C. or above by way of primary stretching, secondary stretching and the like as disclosed in Japanese Patent Publication No. 13399/1968; and a process wherein a primary stretching as mentioned above is carried out at a ratio between a primary point of flection and a secondary point of flection and the stretching is effected at a temperature of 150.degree. to 170.degree. C. as disclosed in Japanese Patent Publication No. 22574/1978.
The PVDF monofilaments obtained by the processes as mentioned above are highly oriented because of stretching and excellent in knot strength and tensile strength, whereas their abrasion resistances are not necessarily satisfactory.